Needleless injectors are used as an alternative to hypodermic syringes to inject drugs and medicaments through a patient's skin into the underlying tissue. A typical injector comprises a high pressure piston pump which dispenses the drug through a small hole with sufficient force to pierce the epidermis and diffuse into the tissues. The present invention is directed to the filling of capsules for use in such injectors.
Axiomatic to the storage of the drug in the capsule is that the filling procedure is compatible with the equipment and protocols established within the pharmaceutical industry, and a number of otherwise promising ideas have failed to become commercialised because this requirement was overlooked. None of the prior art capsules have all of the features necessary for optimum storage of the drug and compatibility with filling machines.
The stringent requirements for ensuring optimum sterility and quality control of drug packaging means that there is a trend towards pre-filling the drug capsule. However, a prefilled capsule must be able to withstand thermal expansion and contraction due to ambient temperature fluctuations. The possible results of the latter is that increased and unacceptable outgassing of the drug could occur, or the drug could expand and leak past the seals.